Fast failover of access points in a split-plane deployment

ABSTRACT

A method, system and computer readable medium for fast failover of an access point are described. A system can cause a failover of a first wireless access point when a wireless control point determines that a first wireless switching plane has failed through a platform link failure mechanism. The system can also prevent a failover of the first wireless access point or a second wireless access point when a message is received from both the first wireless switching plane and a second wireless switching plane indicating that the other wireless switching plane has failed.

TECHNICAL FIELD

Embodiments relate generally to wireless networking, and moreparticularly, to methods, systems and computer readable media for fastfailover of access points in split-plane wireless network deployments.

BACKGROUND

Wireless network deployments models include the overlay deployment modeland the split-plane deployment model. An overlay deployment model is onewireless network deployment model that may be commonly used. An overlaydeployment model can include collocation of wireless control plane (WCP)functions and wireless switching plane (WSP) functions in a singledevice (e.g., a wireless controller or WC). A split-plane deploymentmodel can include WCP functions decoupled from WSP functions, with eachof the WCP and WSP located in a separate device.

Forwarding in a wireless deployment can include distributed forwardingand centralized forwarding. Distributed forwarding can include a specialcase of a split-plane deployment model in which some or all of the WSPfunctionality resides in an access point (AP).

Centralized forwarding can include a deployment in which WSPfunctionality resides outside of the APs. APs forward traffic to adevice that implements the WSP functionality. The overlay deploymentmodel and split-plane deployment model are examples of centralizedforwarding.

SUMMARY

One embodiment includes a wireless network system. The system can have awireless control point, a first wireless switching plane, a secondwireless switching plane, a first wireless access point and a secondwireless access point.

The wireless control point is adapted to cause a failover of the secondwireless access point when the wireless control point determines thatthe first wireless switching plane has failed. The wireless controlpoint is also adapted to not cause a failover of the first wirelessaccess point or the second wireless access point when a message isreceived from both the first wireless switching plane and the secondwireless switching plane indicating that the other wireless switchingplane has failed.

An interswitch trunk line can couple the first wireless switching planewith the second wireless switching plane. The first wireless switchingplane and the second wireless switching plane can communicate over theinterswitch trunk line via a split multi-line trunking protocol. Thesecond wireless switching plane can determine that the first wirelessswitching plane has failed based on an interswitch trunk protocol.

The first wireless switching plane and the second wireless switchingplane can communicate over the interswitch trunk line via a non-splitmulti-line trunking protocol. The second wireless switching plane candetermine that the first wireless switching plane has failed based on alink down event.

Another embodiment is a method for fast failover of access points in asplit-plane wireless network deployment. The method can include causinga failover of a first wireless access point when a wireless controlpoint determines that a first wireless switching plane has failedthrough a platform link failure mechanism. The method can also includepreventing a failover of the first wireless access point or a secondwireless access point when a message is received from both the firstwireless switching plane and a second wireless switching planeindicating that the other wireless switching plane has failed.

The first wireless switching plane and the second wireless switchingplane can communicate over an interswitch trunk line. The method caninclude communicating from the first wireless switching plane to thesecond wireless switching plane over the interswitch trunk line via asplit multi-line trunking protocol.

The method can include determining at the second wireless switchingplane, that the first wireless switching plane has failed based on aninterswitch trunk protocol. The method can also include communicatingbetween the first wireless switching plane and the second wirelessswitching plane over the interswitch trunk line via a non-splitmulti-line trunking protocol. The method can further includedetermining, at the second wireless switching plane, that the firstwireless switching plane has failed based on a link down event.

Yet another embodiment includes a nontransitory computer readable mediumhaving stored thereon software instructions that, when executed by aprocessor, cause the processor to perform a series of operationscomprising.

The processor can cause a failover of a first wireless access point whena wireless control point determines that a first wireless switchingplane has failed through a platform link failure mechanism. Also, thesystem can prevent a failover of the first wireless access point or asecond wireless access point when a message is received from both thefirst wireless switching plane and a second wireless switching planeindicating that each of the other respective wireless switching planeshas failed.

The first wireless switching plane and the second wireless switchingplane can communicate over an interswitch trunk line. The operations canalso include communicating from the first wireless switching plane tothe second wireless switching plane over the interswitch trunk line viaa split multi-line trunking protocol.

The operations can further include determining, at the second wirelessswitching plane, that the first wireless switching plane has failedbased on an interswitch trunk protocol. The operations can also includecommunicating between the first wireless switching plane and the secondwireless switching plane over the interswitch trunk line via a non-splitmulti-line trunking protocol. The operations can also includedetermining, at the second wireless switching plane, that the firstwireless switching plane has failed based on a link down event.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example wireless network with a split planedeployment in accordance with at least one embodiment.

FIG. 2 shows the wireless network of FIG. 1, in which a WSP has failed.

FIG. 3 shows the wireless network of FIG. 1, in which a trunk linebetween WSPs is intermittently down (e.g., flapping).

FIG. 4 is a flow chart showing an example failover method in accordancewith at least one embodiment.

FIG. 5 is a flow chart showing an example method for detecting anintermittent line between WSPs in accordance with at least oneembodiment.

DETAILED DESCRIPTION

In general, an embodiment can include a method, system or computerreadable medium for fast failover of access points in split-planewireless network deployments. WSPs can be coupled via a split multi-linktrunking (SMLT) or a non-SMLT protocol.

As shown in FIG. 1, a wireless network 100 includes a wireless controlpoint (WCP) 102, a first WSP 104, a second WSP 106, a first access point(AP-1) 108, a second access point (AP-2) 110, a first client device 112and a second client device 114.

The WCP 102 can have a control channel connection (shown as dashedlines) to WSP-1 (104), WSP-2 (106), AP-1 (108) and AP-2 (110). WSP-1(104) and WSP-2 (106) can be connected via a link such as an interswitchtrunk (IST). The WSPs (104 and 106) can include an L2/L3 switch. TheL2/L3 switches of the WSPs (104 and 106) can be partially managed by theWCP 102.

The access points (AP-1 and AP-2) can be devices managed by the WCP 102and may not provide standard management interfaces (e.g., console,telnet/SSH, SNMP, HTTP or the like) for device configuration. Accesspoints discover the WCP using a discovery protocol and establish acontrol channel with the WCP.

Configuration information for each access point can be defined on theWCP 102 and pushed to the access point when it associates with the WCPover the control channel. A WCP managed device, such as an access point,applies the received configuration from WCP with which it hasassociated. Also, access points report monitoring information to the WCPwith which it has associated.

The WSPs (WSP-1 and WSP-2) are partially managed by the WCP 102. EachWSP discovers the WCP and establishes a control channel with the WCP.WSPs receive mobility VLAN configuration and state information from themanaging WCP. An example of a WSP is the Avaya ERS 8800. If two WSPs aredirectly connected over IST, the WSPs can be configured to operate asSMLT pairs.

The WSPs (WSP-1 and WSP-2) can use an SMLT or non-SMLT protocol for theconnection between the two WSPs. SMLT is an extension of MLT that allowsedge switches to dual-home to two SMLT aggregation switches. SMLT canprovide link failure protection and flexible bandwidth scaling.

SMLT can help avoid loops by allowing two edge aggregation switches toappear as a single device to the edge switches, which are dual homed toaggregation switches. Further, SMLT networks may not require the use ofspanning tree protocols. The WSPs can be interconnected using an IST,which allows them to exchange address and state information therebypermitting rapid fault detection and forwarding path modification.

In a conventional deployment and configuration, the WSPs may beconnected over an IST trunk and configured to operate as SMLT peers. TheWSPs can discover a WCP and establish a control channel. The APs canalso discover the WCP and establish a control channel.

The WCP may direct a first WSP to reserve resources for a first AP, anda second WSP to reserve resources for a second AP. The WCP can directthe first AP to terminate an access tunnel on the first WSP and thesecond AP to terminate an access tunnel on the second WSP. Assume thatclient devices associate with the first AP. The first AP and the firstWSP program the access tunnel in a client VLAN and clients can send andreceive traffic.

Assume, for this example of a conventional deployment, that the firstWSP fails and the first AP detects the failure through a keep alivetimeout signal or message. The first AP will then make a request to theWCP for a WSP. The WCP may assign the second WSP and direct the secondWSP to reserve resources for the first AP. The WCP may then direct thefirst AP to terminate an access tunnel on the second WSP.

The first AP can establish a tunnel with the second WSP. The first APthen reprograms the access tunnel which is now terminated on the secondWSP on all client VLANs. A problem with the above conventional approachis that the failover may take tens of seconds, during which timecustomer data may be affected.

One solution proposed to the conventional AP failover scenario describedabove is an SMLT assisted failover, which can failover in a subsecondtimeframe. However, the SMLT assisted failover is vulnerable to anintermittent (e.g., flapping) trunk connection. The failover sequencemay be repeated as the trunk flaps.

An embodiment can provide a fast failover for access points in asplit-plane deployment and a robust mechanism that is tolerant offlapping trunk lines.

FIG. 2 shows a wireless network deployment in which WSP-1 104 hasfailed. The flowchart shown in FIG. 4 is an example method for APfailover when a WSP fails and can be understood with reference to FIG.2.

Processing begins at 402, where WSP-2 106 detects a failure of WSP-1 104through a platform link failure mechanism. In an SMLT implementation, anIST protocol could be used by WSP-2 106 to determine that WSP-1 104 hasfailed. In a non-SMLT implementation, a link down event could be used byWSP-2 106 to determine that WSP-1 104 had failed.

At 404, WSP-2 106 communicates the failure of WSP-1 104 to the WCP 102.

At 406, the WCP 102 confirms the failure of WSP-1 104, for example byattempting to communicate with WSP-1 104 and receiving no response.Also, another technique for confirming failure can include the WCP 102waiting for a delta time (e.g., a configurable time in milliseconds) tohear from the WSP-1 104 for the link failure events (with WSP2 106). Ifthe WCP 102 does not receive within the timeout, the WCP concludes thatthe WSP-1 104 is down, and proceeds to inform the APs to failover toWSP-2 106.

At 408, the WCP 102 directs AP-1 108 to terminate an access tunnel onWSP-2 106.

At 410, AP-1 108 updates the access tunnel endpoint to point to WSP-2106 and terminates the tunnel on WSP-2 106.

At 412, AP-1 108 and WSP-2 106 program the access tunnel on all clientVLANs.

The above steps (e.g., 402-412) can be performed in a subsecond timeframe. It will be appreciated that steps 402-412 can be repeated inwhole or in part in order to perform a contemplated access pointfailover task.

FIG. 3 shows a scenario in which the inter switch trunk line betweenWSP-1 104 and WSP-2 106 flaps. FIG. 5 is a flowchart showing an examplemethod of handling a flapping trunk line.

Processing begins at 502, where WSP-2 106 detects what appears to be afailure of WSP-1 104 through a platform link failure mechanism in amanner similar to that described above for 402. However, in the case ofFIGS. 3 and 5, WSP-1 104 has not failed, but rather the trunk linebetween WSP-1 and WSP-2 is flapping.

At 504, WSP-2 106 communicates the detection of a possible failure ofWSP-1 104 to the WCP 102.

At 506, around the same time as 502 and 504, WSP-1 104 detects appearsto be a failure of WSP-2 106 through a platform link failure mechanismin a manner similar to that described above for 402. However, in thecase of FIGS. 3 and 5, WSP-2 106 has not failed, but rather the trunkline between WSP-1 and WSP-2 is flapping.

At 508, WSP-1 104 communicates the possible failure of WSP-2 106 to theWCP 102.

At 510, the WCP 102 determines that the trunk line is flapping becauseWSP-1 104 and WSP-2 106 each reported the other having failed. Becausethe WCP 102 receives reports from both WSPs, it is possible for the WCP102 to determine that both WSPs are in fact functioning and that it isthe trunk line between the two that has failed or become intermittent.Thus, the WCP 102 can determine that no failover and redirection ofaccess points is needed (512).

The above steps (e.g., 502-512) can be performed in a subsecond timeframe. It will be appreciated that steps 502-512 can be repeated inwhole or in part in order to perform a contemplated access pointfailover task.

It will be appreciated that the modules, processes, systems, andsections described above can be implemented in hardware, hardwareprogrammed by software, software instructions stored on a nontransitorycomputer readable medium or a combination of the above. A system foredge network virtualization encapsulation, for example, can include aprocessor configured to execute a sequence of programmed instructionsstored on a nontransitory computer readable medium. For example, theprocessor can include, but not be limited to, a personal computer orworkstation or other such computing system that includes a processor,microprocessor, microcontroller device, or is comprised of control logicincluding integrated circuits such as an Application Specific IntegratedCircuit (ASIC). The instructions can be compiled from source codeinstructions provided in accordance with a programming language such asJava, C, C++, C#.net, assembly or the like. The instructions can alsocomprise code and data objects provided in accordance with, for example,the Visual Basic™ language, or another structured or object-orientedprogramming language. The sequence of programmed instructions, orprogrammable logic device configuration software, and data associatedtherewith can be stored in a nontransitory computer-readable medium suchas a computer memory or storage device which may be any suitable memoryapparatus, such as, but not limited to ROM, PROM, EEPROM, RAM, flashmemory, disk drive and the like.

Furthermore, the modules, processes systems, and sections can beimplemented as a single processor or as a distributed processor.Further, it should be appreciated that the steps mentioned above may beperformed on a single or distributed processor (single and/ormulti-core, or cloud computing system). Also, the processes, systemcomponents, modules, and sub-modules described in the various figures ofand for embodiments above may be distributed across multiple computersor systems or may be co-located in a single processor or system. Examplestructural embodiment alternatives suitable for implementing themodules, sections, systems, means, or processes described herein areprovided below.

The modules, processors or systems described above can be implemented asa programmed general purpose computer, an electronic device programmedwith microcode, a hard-wired analog logic circuit, software stored on acomputer-readable medium or signal, an optical computing device, anetworked system of electronic and/or optical devices, a special purposecomputing device, an integrated circuit device, a semiconductor chip,and/or a software module or object stored on a computer-readable mediumor signal.

Embodiments of the method and system (or their sub-components ormodules), may be implemented on a general-purpose computer, aspecial-purpose computer, a programmed microprocessor or microcontrollerand peripheral integrated circuit element, an ASIC or other integratedcircuit, a digital signal processor, a hardwired electronic or logiccircuit such as a discrete element circuit, a programmed logic circuitsuch as a PLD, PLA, FPGA, PAL, or the like. In general, any processorcapable of implementing the functions or steps described herein can beused to implement embodiments of the method, system, or a computerprogram product (software program stored on a nontransitory computerreadable medium).

Furthermore, embodiments of the disclosed method, system, and computerprogram product (or software instructions stored on a nontransitorycomputer readable medium) may be readily implemented, fully orpartially, in software using, for example, object or object-orientedsoftware development environments that provide portable source code thatcan be used on a variety of computer platforms. Alternatively,embodiments of the disclosed method, system, and computer programproduct can be implemented partially or fully in hardware using, forexample, standard logic circuits or a VLSI design. Other hardware orsoftware can be used to implement embodiments depending on the speedand/or efficiency requirements of the systems, the particular function,and/or particular software or hardware system, microprocessor, ormicrocomputer being utilized. Embodiments of the method, system, andcomputer program product can be implemented in hardware and/or softwareusing any known or later developed systems or structures, devices and/orsoftware by those of ordinary skill in the applicable art from thefunction description provided herein and with a general basic knowledgeof the software engineering and computer networking arts.

Moreover, embodiments of the disclosed method, system, and computerreadable media (or computer program product) can be implemented insoftware executed on a programmed general purpose computer, a specialpurpose computer, a microprocessor, or the like.

It is, therefore, apparent that there is provided, in accordance withthe various embodiments disclosed herein, systems, methods and computerreadable media for fast failover of access points in split-planewireless network deployments.

While the disclosed subject matter has been described in conjunctionwith a number of embodiments, it is evident that many alternatives,modifications and variations would be, or are, apparent to those ofordinary skill in the applicable arts. Accordingly, Applicants intend toembrace all such alternatives, modifications, equivalents and variationsthat are within the spirit and scope of the disclosed subject matter.

What is claimed is:
 1. A wireless network system comprising: a wirelesscontrol point; a first wireless switching plane; a second wirelessswitching plane; a first wireless access point; and a second wirelessaccess point, wherein the wireless control point is adapted to cause afailover of the second wireless access point when the wireless controlpoint determines that the first wireless switching plane has failed, andwherein the wireless control point is adapted to not cause a failover ofthe first wireless access point or the second wireless access point whena message is received from both the first wireless switching plane andthe second wireless switching plane indicating that the other wirelessswitching plane has failed.
 2. The system of claim 1, further comprisingan interswitch trunk line coupling the first wireless switching planewith the second wireless switching plane.
 3. The system of claim 2,wherein the first wireless switching plane and the second wirelessswitching plane communicate over the interswitch trunk line via a splitmulti-line trunking protocol.
 4. The system of claim 3, wherein thesecond wireless switching plane determines the first wireless switchingplane has failed based on an interswitch trunk protocol.
 5. The systemof claim 2, wherein the first wireless switching plane and the secondwireless switching plane communicate over the interswitch trunk line viaa non-split multi-line trunking protocol.
 6. The system of claim 5,wherein the second wireless switching plane determines the firstwireless switching plane has failed based on a link down event.
 7. Amethod for fast failover of access points in a split-plane wirelessnetwork deployment, the method comprising: causing a failover of a firstwireless access point when a wireless control point determines that afirst wireless switching plane has failed through a platform linkfailure mechanism; and preventing a failover of the first wirelessaccess point or a second wireless access point when a message isreceived from both the first wireless switching plane and a secondwireless switching plane indicating that the other wireless switchingplane has failed.
 8. The method of claim 7, wherein the first wirelessswitching plane and the second wireless switching plane communicate overan interswitch trunk line.
 9. The method of claim 8, further comprisingcommunicating from the first wireless switching plane to the secondwireless switching plane over the interswitch trunk line via a splitmulti-line trunking protocol.
 10. The method of claim 9, furthercomprising determining, at the second wireless switching plane, that thefirst wireless switching plane has failed based on an interswitch trunkprotocol.
 11. The method of claim 8, further comprising communicatingbetween the first wireless switching plane and the second wirelessswitching plane over the interswitch trunk line via a non-splitmulti-line trunking protocol.
 12. The method of claim 11, furthercomprising determining, at the second wireless switching plane, that thefirst wireless switching plane has failed based on a link down event.13. A nontransitory computer readable medium having stored thereonsoftware instructions that, when executed by a processor, cause theprocessor to perform a series of operations comprising: causing afailover of a first wireless access point when a wireless control pointdetermines that a first wireless switching plane has failed through aplatform link failure mechanism; and preventing a failover of the firstwireless access point or a second wireless access point when a messageis received from both the first wireless switching plane and a secondwireless switching plane indicating that the other wireless switchingplane has failed.
 14. The nontransitory computer readable medium ofclaim 13, wherein the first wireless switching plane and the secondwireless switching plane communicate over an interswitch trunk line. 15.The nontransitory computer readable medium of claim 14, wherein theoperations further comprise communicating from the first wirelessswitching plane to the second wireless switching plane over theinterswitch trunk line via a split multi-line trunking protocol.
 16. Thenontransitory computer readable medium of claim 15, further comprisingdetermining, at the second wireless switching plane, that the firstwireless switching plane has failed based on an interswitch trunkprotocol.
 17. The nontransitory computer readable medium of claim 14,further comprising communicating between the first wireless switchingplane and the second wireless switching plane over the interswitch trunkline via a non-split multi-line trunking protocol.
 18. The nontransitorycomputer readable medium of claim 17, further comprising determining, atthe second wireless switching plane, that the first wireless switchingplane has failed based on a link down event.